This invention relates to an electrochromic device utilizing electrochromism.
An electrochromic device such as a smart window utilizing electrochromic materials is expected to be used for a wide variety of usage. However, the conventional electrochromic devices have a drawback in that they are easily deteriorated in the environment wherein ultraviolet rays are irradiated such as the outdoors.
In order to prevent the deterioration, it is suggested, for example, to provide a ultraviolet shielding layer outside a substrate constituting the smart window. However, this is not a satisfying solution in respect of appearance, wear resistance, and durability.
In an electrochromic device, usually a pair of transparent electrodes are disposed between a pair of transparent substrates, between which an electrochromic layer and an electrolyte layer are placed. It is suggested to provide an ultraviolet shielding layer inside the transparent electrodes to prevent the deterioration by ultraviolet irradiation (Japanese Laid-open Patent Application Nos. 62-148339 and 63-236016). This method does not adversely affect the abrasion resistance of the transparent substrate constituting the device. However, when the ultraviolet shielding layer is composed of metal oxides (Japanese Laid-open Patent Application No. 62-148339), near-ultraviolet area cannot be cut sufficiently, and thus the deterioration by ultraviolet rays cannot be prohibited satisfactory. Alternatively, when a dichroic layer is adopted as a ultraviolet shielding layer (Japanese Laid-open Patent Application No. 63-236016), a number of processes are required, thus being disadvantageous in cost.